Cover Feature: The Gallate Pnictides Ba9[GaO4]3Pn (Pn=Sb, Bi) and a Partially Oxidized Zintl Anion in Ba2[GaO2As] (Z. Anorg. Allg. Chem. 10/2022)

Abstract

The cover picture shows a section of the the chain of connected GaO2As2 tetrahedra in the crystal of Ba2[GaO2As] and the coordination polyhedron of the As atom by surrounding Ba ions. This [–O2Ga–As–4−]n polyanion reminds of a typical Zintl phase with covalent triele–pnictide bonds in the infinite Ga–As chain. The incorporation of oxygen bound to a constituent of the polyanion is a rare and unique structural feature. One can perceive this compound as a Zintl phase with a partially oxidized polyanion. S. Klos et al. describe in their article the access to a new class of metallate-metallides in the system Ba/Ga/Pn/O (Pn=As, Sb, Bi) by adding sub-stochiometric amounts of BaO2 as the oxygen source to mixtures of Ba, Ga, and one of the pnictide elements. With the heavier pnictides Sb and Bi, Ba9[GaO4]3Pn is formed with a different structure type containing oxogallate anions [GaO4]5− encapsulating discrete Sb3− and Bi3− ions. (DOI: 10.1002/zaac.202100363).